Polyimide is a polymer having two imide rings in the backbone and fabricated by condensation-polymerization of tetracarboxyl acid and diamine.
Polyimide is of commercial importance because it has excellent light transmissivity, excellent mechanical properties, excellent thermal characteristics, and an excellent adhesive strength with a substrate. Polyimide is widely used in the various fields, such as electricity, electron, cars, airplanes, and semiconductors, instead of metal and glass.
In particular, polyimide is used for a surface protection film or an insulating film of a semiconductor device because of its excellent thermal characteristics and mechanical properties. Most polyimide has a low solubility and thus polyimide is chiefly fabricated using a method comprising obtaining a polyimide precursor solution, coating the polyimide precursor solution on a substrate made of glass, etc., and performing curing using heat treatment. Commercialized polyimide products are supplied in the form of a polyimide precursor solution or a polyimide film. In the field of semiconductor devices, the polyimide products are chiefly supplied in the form of a polyimide precursor solution.
A photosensitive polyimide composition is required to have photo sensitivity and must not cause a crack in a protection film so that it can bear up against a device manufacturing process such as a semiconductor manufacturing process. To this end, it is important to select a synthesis monomer for fabricating a polyimide precursor having excellent light transmissivity and resolution, but not causing a crack in the final device manufacturing process.